bims-mimbat 2023-07-09 papers

bims-mimbat

Biomed News

on Mitochondrial metabolism in brown adipose tissue

Issue of 2023–07–09
eleven papers selected by
José Carlos de Lima-Júnior, Washington University

Respiratory complex I in mitochondrial membrane catalyzes oversized ubiquinones.
Genistein-mediated thermogenesis and white-to-beige adipocyte differentiation involve transcriptional activation of cAMP response elements in the Ucp1 promoter.
Becoming less beige with age.
ISRIB alleviates aging-associated brown fat UCP1 translational repression and thermogenic deficiency.
Hepatocellular carcinoma induced by hepatocyte Pten deletion reduces BAT UCP-1 and thermogenic capacity in mice, despite increasing serum FGF-21 and iWAT browning.
Transient protonic capacitor: Explaining the bacteriorhodopsin membrane experiment of Heberle et al. 1994.
Linker histone variant H1.2 is a brake on white adipose tissue browning.
Arf1 coordinates fatty acid metabolism and mitochondrial homeostasis.
Uncharacterized protein C17orf80: A novel interactor of human mitochondrial nucleoids.
Endothelial cell CD36 regulates membrane ceramide formation, exosome fatty acid transfer and circulating fatty acid levels.
Proximity-labeling chemoproteomics defines the subcellular cysteinome and inflammation-responsive mitochondrial redoxome.

J Biol Chem. 2023 Jun 30. pii: S0021-9258(23)02029-X. [Epub ahead of print] 105001

Respiratory complex I in mitochondrial membrane catalyzes oversized ubiquinones.

Ryo Ikunishi, Ryohei Otani, Takahiro Masuya, Kyoko Shinzawa-Itoh, Tomoo Shiba, Masatoshi Murai, Hideto Miyoshi.

  NADH-ubiquinone (UQ) oxidoreductase (complex I) couples electron transfer from NADH to UQ with proton translocation in its membrane part. The UQ reduction step is key to triggering proton translocation. Structural studies have identified a long, narrow, tunnel-like cavity within complex I, through which UQ may access a deep reaction site. To elucidate the physiological relevance of this UQ-accessing tunnel, we previously investigated whether a series of oversized UQs (OS-UQs), whose tail moiety is too large to enter and transit the narrow tunnel, can be catalytically reduced by complex I using the native enzyme in bovine heart submitochondrial particles (SMPs) and the isolated enzyme reconstituted into liposomes. Nevertheless, the physiological relevance remained unclear because some amphiphilic OS-UQs were reduced in SMPs but not in proteoliposomes, and investigation of extremely hydrophobic OS-UQs was not possible in SMPs. To uniformly assess the electron transfer activities of all OS-UQs with the native complex I, here we present a new assay system using SMPs, which were fused with liposomes incorporating OS-UQ and supplemented with a parasitic quinol oxidase to recycle reduced OS-UQ. In this system, all OS-UQs tested were reduced by the native enzyme, and the reduction was coupled with proton translocation. This finding does not support the canonical tunnel model. We propose that the UQ reaction cavity is flexibly open in the native enzyme to allow OS-UQs to access the reaction site, but their access is obstructed in the isolated enzyme as the cavity is altered by detergent-solubilizing from the mitochondrial membrane.

Keywords:  bioenergetics; chemical biology; complex I; respiratory enzymes; ubiquinone

DOI:  https://doi.org/10.1016/j.jbc.2023.105001
FASEB J. 2023 Aug;37(8): e23079

Genistein-mediated thermogenesis and white-to-beige adipocyte differentiation involve transcriptional activation of cAMP response elements in the Ucp1 promoter.

Rebeca Fuentes-Romero, Laura A Velázquez-Villegas, Sarai Vasquez-Reyes, Berenice Pérez-Jiménez, Zuleima N Domínguez Velázquez, Mónica Sánchez-Tapia, Ariana Vargas-Castillo, Sandra Tobón-Cornejo, Adriana M López-Barradas, Valentín Mendoza, Nimbe Torres, Fernando López-Casillas, Armando R Tovar.

Genistein is an isoflavone present in soybeans and is considered a bioactive compound due to its widely reported biological activity. We have previously shown that intraperitoneal genistein administration and diet supplementation activates the thermogenic program in rats and mice subcutaneous white adipose tissue (scWAT) under multiple environmental cues, including cold exposure and high-fat diet feeding. However, the mechanistic insights of this process were not previously unveiled. Uncoupling protein 1 (UCP1), a mitochondrial membrane polypeptide responsible for dissipating energy into heat, is considered the most relevant thermogenic marker; thus, we aimed to evaluate whether genistein regulates UCP1 transcription. Here we show that genistein administration to thermoneutral-housed mice leads to the appearance of beige adipocyte markers, including a sharp upregulation of UCP1 expression and protein abundance in scWAT. Reporter assays showed an increase in UCP1 promoter activity after genistein stimulation, and in silico analysis revealed the presence of estrogen (ERE) and cAMP (CRE) response elements as putative candidates of genistein activation. Mutation of the CRE but not the ERE reduced genistein-induced promoter activity by 51%. Additionally, in vitro and in vivo ChIP assays demonstrated the binding of CREB to the UCP1 promoter after acute genistein administration. Taken together, these data elucidate the mechanism of genistein-mediated UCP1 induction and confirm its potential applications in managing metabolic disorders.

DOI: https://doi.org/10.1096/fj.202300139RR
Elife. 2023 Jul 07. pii: e89700. [Epub ahead of print]12

Becoming less beige with age.

Anying Song, Qiong A Wang.

  The production of beige adipocytes following cold exposure is blocked as mice get older and leads to changes in the expression of metabolic genes.

Keywords:  adipocytes; ageing; cell biology; cold exposure; metabolism; mouse

DOI:  https://doi.org/10.7554/eLife.89700
Biochem Biophys Res Commun. 2023 Jun 24. pii: S0006-291X(23)00828-8. [Epub ahead of print]673 179-186

ISRIB alleviates aging-associated brown fat UCP1 translational repression and thermogenic deficiency.

Muze Li, Mengjie Gao, Meiqi Jia, Yifan Lu, Yue Zhai, Huanyu Lu.

  Upon cold exposure, aged people with lower metabolic rate cannot rapidly increase the higher levels of heat production, and are seriously threatened by the hypothermia, extensive cold stress responses and risk of mortality. Here, we show that brown fat thermogenic activity is obviously deficient in aged mice, associating with reduction of UCP1 expression and inhibition of its mRNA translation. As we considered, aging aggravates brown fat oxidative stress and activates the integrated stress response (ISR), inducing the phosphorylation of eIF2α to block the global mRNA translation. Therefore, small-molecule ISR inhibitor (ISRIB) treatment attenuates the higher level of eIF2α phosphorylation, restores the repression of Ucp1 mRNA translation and improves UCP1-mediated thermogenic function to defend cold stress in aged mice. Furthermore, ISRIB treatment increases the relative lower metabolic rates, and alleviates glucose intolerance and insulin resistance in aged mice. Thus, we have uncovered a promising drug that reverses the aged-related the deficiency of UCP1-mediated thermogenesis to combat cold stress and associated metabolic diseases.

Keywords:  Aging; Brown fat; ISRIB; Thermogenesis; Translational efficiency; UCP1

DOI:  https://doi.org/10.1016/j.bbrc.2023.06.073
J Physiol Biochem. 2023 Jul 05.

Hepatocellular carcinoma induced by hepatocyte Pten deletion reduces BAT UCP-1 and thermogenic capacity in mice, despite increasing serum FGF-21 and iWAT browning.

Álbert S Peixoto, Mayara F Moreno, Érique Castro, Luiz A Perandini, Thiago Belchior, Tiago E Oliveira, Thayna S Vieira, Gustavo R Gilio, Caroline A Tomazelli, Bianca F Leonardi, Milene Ortiz-Silva, Luciano P Silva Junior, Eduardo H Moretti, Alexandre A Steiner, William T Festuccia.

  Hepatocellular carcinoma (HCC) markedly enhances liver secretion of fibroblast growth factor 21 (FGF-21), a hepatokine that increases brown and subcutaneous inguinal white adipose tissues (BAT and iWAT, respectively) uncoupling protein 1 (UCP-1) content, thermogenesis and energy expenditure. Herein, we tested the hypothesis that an enhanced BAT and iWAT UCP-1-mediated thermogenesis induced by high levels of FGF-21 is involved in HCC-associated catabolic state and fat mass reduction. For this, we evaluated body weight and composition, liver mass and morphology, serum and tissue levels of FGF-21, BAT and iWAT UCP-1 content, and thermogenic capacity in mice with Pten deletion in hepatocytes that display a well-defined progression from steatosis to steatohepatitis (NASH) and HCC upon aging. Hepatocyte Pten deficiency promoted a progressive increase in liver lipid deposition, mass, and inflammation, culminating with NASH at 24 weeks and hepatomegaly and HCC at 48 weeks of age. NASH and HCC were associated with elevated liver and serum FGF-21 content and iWAT UCP-1 expression (browning), but reduced serum insulin, leptin, and adiponectin levels and BAT UCP-1 content and expression of sympathetically regulated gene glycerol kinase (GyK), lipoprotein lipase (LPL), and fatty acid transporter protein 1 (FATP-1), which altogether resulted in an impaired whole-body thermogenic capacity in response to CL-316,243. In conclusion, FGF-21 pro-thermogenic actions in BAT are context-dependent, not occurring in NASH and HCC, and UCP-1-mediated thermogenesis is not a major energy-expending process involved in the catabolic state associated with HCC induced by Pten deletion in hepatocytes.

Keywords:  Brown adipose tissue; Energy expenditure; Nonalcoholic fatty liver disease; Thermogenic capacity; UCP-1; White adipose tissue browning

DOI:  https://doi.org/10.1007/s13105-023-00970-4
Biophys Chem. 2023 Jun 28. pii: S0301-4622(23)00123-0. [Epub ahead of print]300 107072

Transient protonic capacitor: Explaining the bacteriorhodopsin membrane experiment of Heberle et al. 1994.

James Weifu Lee.

  The transmembrane-electrostatically localized protons (TELP) theory can serve as a unified framework to explain experimental observations and elucidate bioenergetic systems including both delocalized and localized protonic coupling. With the TELP model as a unified framework, it is now better explained how the bacteriorhodopsin-purple membrane-ATPase system functions. The bacteriorhodopsin pumping of protons across the membrane results in the formation of TELP around the halobacterial extracellular membrane surface that is perfectly positioned to drive ATP synthase for the synthesis of ATP from ADP and Pi. The bacteriorhodopsin purple membrane sheet experiment of Heberle et al. 1994 is now better explained here as a transient "protonic capacitor". During the lifetime of a flashlight-induced protonic bacteriorhodopsin purple membrane capacitor activity, there is at least a transient non-zero membrane potential (Δψ ≠ 0). The experimental results demonstrated that "after proton release by an integral membrane protein, long-range proton transfer along the membrane surface is faster than proton exchange with the bulk water phase" exactly as predicted by the TELP theory, which is fundamentally important to the science of bioenergetics.

Keywords:  ATP synthesis; Excess protons; Local protonic motive force; Proton “hops and turns” mechanism; Protonic conductor; Transmembrane-electrostatically localized protons

DOI:  https://doi.org/10.1016/j.bpc.2023.107072
Nat Commun. 2023 Jul 06. 14(1): 3982

Linker histone variant H1.2 is a brake on white adipose tissue browning.

Yangmian Yuan, Yu Fan, Yihao Zhou, Rong Qiu, Wei Kang, Yu Liu, Yuchen Chen, Chenyu Wang, Jiajian Shi, Chengyu Liu, Yangkai Li, Min Wu, Kun Huang, Yong Liu, Ling Zheng.

Adipose-tissue is a central metabolic organ for whole-body energy homeostasis. Here, we find that highly expressed H1.2, a linker histone variant, senses thermogenic stimuli in beige and brown adipocytes. Adipocyte H1.2 regulates thermogenic genes in inguinal white-adipose-tissue (iWAT) and affects energy expenditure. Adipocyte H1.2 deletion (H1.2AKO) male mice show promoted iWAT browning and improved cold tolerance; while overexpressing H1.2 shows opposite effects. Mechanistically, H1.2 binds to the promoter of Il10rα, which encodes an Il10 receptor, and positively regulates its expression to suppress thermogenesis in a beige cell autonomous manner. Il10rα overexpression in iWAT negates cold-enhanced browning of H1.2AKO male mice. Increased H1.2 level is also found in WAT of obese humans and male mice. H1.2AKO male mice show alleviated fat accumulation and glucose intolerance in long-term normal chow-fed and high fat diet-fed conditions; while Il10rα overexpression abolishes these effects. Here, we show a metabolic function of H1.2-Il10rα axis in iWAT.

DOI: https://doi.org/10.1038/s41467-023-39713-w
Nat Cell Biol. 2023 Jul 03.

Arf1 coordinates fatty acid metabolism and mitochondrial homeostasis.

Ludovic Enkler, Viktoria Szentgyörgyi, Mirjam Pennauer, Cristina Prescianotto-Baschong, Isabelle Riezman, Aneta Wiesyk, Reut Ester Avraham, Martin Spiess, Einat Zalckvar, Roza Kucharczyk, Howard Riezman, Anne Spang.

Lipid mobilization through fatty acid β-oxidation is a central process essential for energy production during nutrient shortage. In yeast, this catabolic process starts in the peroxisome from where β-oxidation products enter mitochondria and fuel the tricarboxylic acid cycle. Little is known about the physical and metabolic cooperation between these organelles. Here we found that expression of fatty acid transporters and of the rate-limiting enzyme involved in β-oxidation is decreased in cells expressing a hyperactive mutant of the small GTPase Arf1, leading to an accumulation of fatty acids in lipid droplets. Consequently, mitochondria became fragmented and ATP synthesis decreased. Genetic and pharmacological depletion of fatty acids phenocopied the arf1 mutant mitochondrial phenotype. Although β-oxidation occurs in both mitochondria and peroxisomes in mammals, Arf1's role in fatty acid metabolism is conserved. Together, our results indicate that Arf1 integrates metabolism into energy production by regulating fatty acid storage and utilization, and presumably organelle contact sites.

DOI: https://doi.org/10.1038/s41556-023-01180-2
J Cell Sci. 2023 Jul 04. pii: jcs.260822. [Epub ahead of print]

Uncharacterized protein C17orf80: A novel interactor of human mitochondrial nucleoids.

Alisa Potter, Anu Hangas, Steffi Goffart, Martijn A Huynen, Alfredo Cabrera-Orefice, Johannes N Spelbrink.

  Molecular functions of many human proteins remain unstudied, despite the demonstrated association with diseases or pivotal molecular structures, such as mitochondrial DNA (mtDNA). This small genome is crucial for proper functioning of mitochondria, the energy-converting organelles. In mammals, mtDNA is arranged into macromolecular complexes called nucleoids that serve as functional stations for its maintenance and expression. Here, we aimed to explore an uncharacterized protein C17orf80, which was previously detected close to the nucleoid components by proximity-labelling mass spectrometry. To investigate the subcellular localization and function of C17orf80, we took an advantage of immunofluorescence microscopy, interaction proteomics and several biochemical assays. We demonstrate that C17orf80 is a mitochondrial membrane-associated protein that interacts with nucleoids even when mtDNA replication is inhibited. In addition, we show that C17orf80 is not essential for mtDNA maintenance and mitochondrial gene expression in cultured human cells. These results provide a basis for uncovering the molecular function of C17orf80 and the nature of its association with nucleoids, possibly leading to new insights about mtDNA and its expression.

Keywords:  2'; 3'-dideoxycytidine; C17orf80; Mitochondria; Mitochondrial nucleoid; mtDNA

DOI:  https://doi.org/10.1242/jcs.260822
Nat Commun. 2023 Jul 07. 14(1): 4029

Endothelial cell CD36 regulates membrane ceramide formation, exosome fatty acid transfer and circulating fatty acid levels.

V S Peche, T A Pietka, M Jacome-Sosa, D Samovski, H Palacios, G Chatterjee-Basu, A C Dudley, W Beatty, G A Meyer, I J Goldberg, N A Abumrad.

Endothelial cell (EC) CD36 controls tissue fatty acid (FA) uptake. Here we examine how ECs transfer FAs. FA interaction with apical membrane CD36 induces Src phosphorylation of caveolin-1 tyrosine-14 (Cav-1Y14) and ceramide generation in caveolae. Ensuing fission of caveolae yields vesicles containing FAs, CD36 and ceramide that are secreted basolaterally as small (80-100 nm) exosome-like extracellular vesicles (sEVs). We visualize in transwells EC transfer of FAs in sEVs to underlying myotubes. In mice with EC-expression of the exosome marker emeraldGFP-CD63, muscle fibers accumulate circulating FAs in emGFP-labeled puncta. The FA-sEV pathway is mapped through its suppression by CD36 depletion, blocking actin-remodeling, Src inhibition, Cav-1Y14 mutation, and neutral sphingomyelinase 2 inhibition. Suppression of sEV formation in mice reduces muscle FA uptake, raises circulating FAs, which remain in blood vessels, and lowers glucose, mimicking prominent Cd36-/- mice phenotypes. The findings show that FA uptake influences membrane ceramide, endocytosis, and EC communication with parenchymal cells.

DOI: https://doi.org/10.1038/s41467-023-39752-3
Cell Chem Biol. 2023 Jun 22. pii: S2451-9456(23)00186-1. [Epub ahead of print]

Proximity-labeling chemoproteomics defines the subcellular cysteinome and inflammation-responsive mitochondrial redoxome.

Tianyang Yan, Ashley R Julio, Miranda Villanueva, Anthony E Jones, Andréa B Ball, Lisa M Boatner, Alexandra C Turmon, Kaitlyn B Nguyễn, Stephanie L Yen, Heta S Desai, Ajit S Divakaruni, Keriann M Backus.

  Proteinaceous cysteines function as essential sensors of cellular redox state. Consequently, defining the cysteine redoxome is a key challenge for functional proteomic studies. While proteome-wide inventories of cysteine oxidation state are readily achieved using established, widely adopted proteomic methods such as OxICAT, Biotin Switch, and SP3-Rox, these methods typically assay bulk proteomes and therefore fail to capture protein localization-dependent oxidative modifications. Here we establish the local cysteine capture (Cys-LoC) and local cysteine oxidation (Cys-LOx) methods, which together yield compartment-specific cysteine capture and quantitation of cysteine oxidation state. Benchmarking of the Cys-LoC method across a panel of subcellular compartments revealed more than 3,500 cysteines not previously captured by whole-cell proteomic analysis. Application of the Cys-LOx method to LPS-stimulated immortalized murine bone marrow-derived macrophages (iBMDM), revealed previously unidentified, mitochondrially localized cysteine oxidative modifications upon pro-inflammatory activation, including those associated with oxidative mitochondrial metabolism.

Keywords:  TurboID; chemoproteomics; cysteine; cysteine oxidation; lipopolysaccharide; macrophages; mitochondria; proximity labeling

DOI:  https://doi.org/10.1016/j.chembiol.2023.06.008